1. Field of the Invention
The present invention relates to a tool holder device for attaching a cutting tool to a machine tool.
2. Discussion of the Prior Art
An example of a known tool holder device is shown in FIG. 18. This tool holder device includes: 1) a first member 204 having a first flat surface 200 and an engaging projection 202 which protrudes from the first flat surface 200 in a direction perpendicular to the first flat surface 200; and 2) a second member 210 having a second flat surface 206 for close contact with the first flat surface 200, and an engaging bore 208 which is engageable with the engaging projection 202. The second member has a tapped hole 212 formed through the cylindrical wall which defines the engaging bore 208. The tapped hole 212 extends in parallel with the second flat surface 206, for engagement with an externally threaded member 214. The threaded member 214 engaging the tapped hole 212 has a truncated conical end 216 on the side of the bore 208, and a tool engaging hole 218 formed at the other end. The second member has another tapped hole 220 formed in line with the tapped hole 212 in a diametrical opposite direction with respect to the bore 208. This tapped hole 220 receives another externally threaded member 222, which has a truncated conical recess 224 formed at one end thereof on the side of the bore 208.
On the other hand, the first member 204 has a through-hole 230 formed through the engaging projection 202, in parallel with the first flat surface 200. In this through-hole 230, there is slidably received a sliding pin 232. The sliding pin has a length shorter than that of the through-hole 230, and has a truncated conical end 234 adjacent to the truncated conical recess 224 of the externally threaded member 222, and a truncated conical recess 236 at the other end adjacent to the truncated conical end 216 of the externally threaded member 214. These truncated conical end and recess 234, 236 are eccentric with the externally threaded members 222, 214.
The first member 204 has a positioning pin 240 screwed in a tapped hole formed in the first flat surface 200 so as to extend in parallel with the engaging projection 202. The positioning pin 240 engages a hole 242 formed in the second flat surface 206, for positioning the first and second members 204, 210 relative to each other in the circumferential direction, so that the externally threaded members 214, 222 and the sliding pin 232 are aligned with each other in the same plane which passes the axes of the two members 204, 210.
A cutting tool is attached to one of the first and second members 204, 210, while the other member is attached to a machine tool. The first member 204 is attached to the second member 210 such that the engaging projection 20 engages the engaging bore 208 while the positioning pin 240 engages the hole 242. In this condition, the externally threaded member 214 is rotated by a suitable tool such as a hexagon wrench key inserted in the tool engaging hole 218, so that the member 214 is moved until the truncated conical end 216 comes into contact with a surface of the truncated conical recess 236 of the sliding pin 232. The threaded member 214 is further rotated to move the sliding pin 232 until the truncated conical end 234 of the pin 232 comes into contact with a surface of the truncated conical recess 224 of the threaded member 222. As a result, the engaging projection 202 is slightly moved in the direction away from the first member 204, due to the effect of the inclined surfaces of the truncated conical ends and recesses 216, 236, 234, 224, so that the first and second flat surfaces 200, 206 are forced against each other for tight contact thereof. Thus, the cutting tool is attached to the machine tool.
In the tool holder device described above, the sliding pin 232 is disposed in the first member 204 while the externally threaded members 214, 222 are incorporated in the second member 210. If, for example, the first member 204 is used as an adaptor to be attached to a spindle of a machine took while the second member 210 is used as a tool holder for supporting a cutting tool, the two threaded members 214, 222 should be provided in each of the second members 210 used as the tool holders for individual different cutting tools which are selectively attached to the machine spindle. Consequently, the required total number of the threaded members 214, 222 and the cost of the tool holders increase with the number of the cutting tools to be used. Further, the sliding pin 232 provided in the first member 204 used as the adaptor to be attached to the machine spindle disturbs an operation to remove cutting chips and any other foreign matters deposited on the adaptor 204 upon changing of the cutting tools from one kind to another. Similar drawbacks are encountered when the first member 204 is used as the tool holder for supporting the cutting tool while the second member 210 is used as the adaptor attached to the machine spindle.